Optimize JSX import source detection (#5498)

* Optimize JSX import source detection

* Skip type import check

3 files changed, 66 insertions, 68 deletions

diff --git a/.changeset/wicked-dolphins-design.md b/.changeset/wicked-dolphins-design.md
new file mode 100644
index 000000000..96236ebb4
--- /dev/null
+++ b/.changeset/wicked-dolphins-design.md
@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+Optimize JSX import source detection
diff --git a/packages/astro/src/vite-plugin-jsx/import-source.ts b/packages/astro/src/vite-plugin-jsx/import-source.ts
new file mode 100644
index 000000000..f21d2ba02
--- /dev/null
+++ b/packages/astro/src/vite-plugin-jsx/import-source.ts
@@ -0,0 +1,59 @@
+import { TsConfigJson } from 'tsconfig-resolver';
+import { AstroRenderer } from '../@types/astro';
+import { parseNpmName } from '../core/util.js';
+
+export async function detectImportSource(
+	code: string,
+	jsxRenderers: Map<string, AstroRenderer>,
+	tsConfig?: TsConfigJson
+): Promise<string | undefined> {
+	let importSource = detectImportSourceFromComments(code);
+	if (!importSource && /import/.test(code)) {
+		importSource = await detectImportSourceFromImports(code, jsxRenderers);
+	}
+	if (!importSource && tsConfig) {
+		importSource = tsConfig.compilerOptions?.jsxImportSource;
+	}
+	return importSource;
+}
+
+// Matches import statements and dynamic imports. Captures import specifiers only.
+// Adapted from: https://github.com/vitejs/vite/blob/97f8b4df3c9eb817ab2669e5c10b700802eec900/packages/vite/src/node/optimizer/scan.ts#L47-L48
+const importsRE =
+	/(?<!\/\/.*)(?<=^|;|\*\/)\s*(?:import(?!\s+type)(?:[\w*{}\n\r\t, ]+from)?\s*("[^"]+"|'[^']+')\s*(?=$|;|\/\/|\/\*)|import\s*\(\s*("[^"]+"|'[^']+')\s*\))/gm;
+
+/**
+ * Scan a file's imports to detect which renderer it may need.
+ * ex: if the file imports "preact", it's safe to assume the
+ * component should be built as a Preact component.
+ * If no relevant imports found, return undefined.
+ */
+async function detectImportSourceFromImports(
+	code: string,
+	jsxRenderers: Map<string, AstroRenderer>
+): Promise<string | undefined> {
+	let m;
+	importsRE.lastIndex = 0;
+	while ((m = importsRE.exec(code)) != null) {
+		const spec = (m[1] || m[2]).slice(1, -1);
+		const pkg = parseNpmName(spec);
+		if (pkg && jsxRenderers.has(pkg.name)) {
+			return pkg.name;
+		}
+	}
+}
+
+/**
+ * Scan a file for an explicit @jsxImportSource comment.
+ * If one is found, return it's value. Otherwise, return undefined.
+ */
+function detectImportSourceFromComments(code: string): string | undefined {
+	// if no imports were found, look for @jsxImportSource comment
+	const multiline = code.match(/\/\*\*?[\S\s]*\*\//gm) || [];
+	for (const comment of multiline) {
+		const [_, lib] = comment.slice(0, -2).match(/@jsxImportSource\s*(\S+)/) || [];
+		if (lib) {
+			return lib.trim();
+		}
+	}
+}
diff --git a/packages/astro/src/vite-plugin-jsx/index.ts b/packages/astro/src/vite-plugin-jsx/index.ts
index 0a3e64344..39be6db6e 100644
--- a/packages/astro/src/vite-plugin-jsx/index.ts
+++ b/packages/astro/src/vite-plugin-jsx/index.ts
@@ -1,23 +1,17 @@
 import type { TransformResult } from 'rollup';
-import type { TsConfigJson } from 'tsconfig-resolver';
 import type { Plugin, ResolvedConfig } from 'vite';
 import type { AstroRenderer, AstroSettings } from '../@types/astro';
 import type { LogOptions } from '../core/logger/core.js';
 import type { PluginMetadata } from '../vite-plugin-astro/types';
 
 import babel from '@babel/core';
-import * as eslexer from 'es-module-lexer';
 import esbuild from 'esbuild';
 import * as colors from 'kleur/colors';
 import path from 'path';
 import { error } from '../core/logger/core.js';
 import { removeQueryString } from '../core/path.js';
-import { parseNpmName } from '../core/util.js';
 import tagExportsPlugin from './tag.js';
-
-type FixedCompilerOptions = TsConfigJson.CompilerOptions & {
-	jsxImportSource?: string;
-};
+import { detectImportSource } from './import-source.js';
 
 const JSX_EXTENSIONS = new Set(['.jsx', '.tsx', '.mdx']);
 const IMPORT_STATEMENTS: Record<string, string> = {
@@ -27,10 +21,6 @@ const IMPORT_STATEMENTS: Record<string, string> = {
 	astro: "import 'astro/jsx-runtime'",
 };
 
-// A code snippet to inject into JS files to prevent esbuild reference bugs.
-// The `tsx` loader in esbuild will remove unused imports, so we need to
-// be careful about esbuild not treating h, React, Fragment, etc. as unused.
-const PREVENT_UNUSED_IMPORTS = ';;(React,Fragment,h);';
 // A fast check regex for the import keyword. False positives are okay.
 const IMPORT_KEYWORD_REGEX = /import/;
 
@@ -46,53 +36,6 @@ function collectJSXRenderers(renderers: AstroRenderer[]): Map<string, AstroRende
 	);
 }
 
-/**
- * Scan a file for an explicit @jsxImportSource comment.
- * If one is found, return it's value. Otherwise, return undefined.
- */
-function detectImportSourceFromComments(code: string): string | undefined {
-	// if no imports were found, look for @jsxImportSource comment
-	const multiline = code.match(/\/\*\*?[\S\s]*\*\//gm) || [];
-	for (const comment of multiline) {
-		const [_, lib] = comment.slice(0, -2).match(/@jsxImportSource\s*(\S+)/) || [];
-		if (lib) {
-			return lib.trim();
-		}
-	}
-}
-
-/**
- * Scan a file's imports to detect which renderer it may need.
- * ex: if the file imports "preact", it's safe to assume the
- * component should be built as a Preact component.
- * If no relevant imports found, return undefined.
- */
-async function detectImportSourceFromImports(
-	code: string,
-	id: string,
-	jsxRenderers: Map<string, AstroRenderer>
-) {
-	// We need valid JS to scan for imports.
-	// NOTE: Because we only need imports, it is okay to use `h` and `Fragment` as placeholders.
-	const { code: jsCode } = await esbuild.transform(code + PREVENT_UNUSED_IMPORTS, {
-		loader: getEsbuildLoader(path.extname(id)) as esbuild.Loader,
-		jsx: 'transform',
-		jsxFactory: 'h',
-		jsxFragment: 'Fragment',
-		sourcefile: id,
-		sourcemap: 'inline',
-	});
-	const [imports] = eslexer.parse(jsCode);
-	if (imports.length > 0) {
-		for (let { n: spec } of imports) {
-			const pkg = spec && parseNpmName(spec);
-			if (!pkg) continue;
-			if (jsxRenderers.has(pkg.name)) {
-				return pkg.name;
-			}
-		}
-	}
-}
 interface TransformJSXOptions {
 	code: string;
 	id: string;
@@ -229,16 +172,7 @@ export default function jsx({ settings, logging }: AstroPluginJSXOptions): Plugi
 				});
 			}
 
-			let importSource = detectImportSourceFromComments(code);
-			if (!importSource && IMPORT_KEYWORD_REGEX.test(code)) {
-				importSource = await detectImportSourceFromImports(code, id, jsxRenderers);
-			}
-
-			// Check the tsconfig
-			if (!importSource) {
-				const compilerOptions = settings.tsConfig?.compilerOptions;
-				importSource = (compilerOptions as FixedCompilerOptions | undefined)?.jsxImportSource;
-			}
+			const importSource = await detectImportSource(code, jsxRenderers, settings.tsConfig);
 
 			// if we still can’t tell the import source, now is the time to throw an error.
 			if (!importSource && defaultJSXRendererEntry) {